Welding seam back-up extrusion



FIG. 1 is a perspective view, of indeterminate length, showing my new design for a welding seam back-up extrusion;

FIG. 2 is a fragmentary top plan view;

FIG. 3 is an end elevational view;

FIG. 4 is a fragmentary elevational view of the rear side, as shown in FIG. 1; and

FIG. 5 is a fragmentary bottom plan view. 

The ornamental design for a welding seam back-up extrusion, as shown and described. 